The cytochrome oxidase and acetylcholinesterase activities were assayed during short and long term ischemia as well as in various recovery periods after 1 hour of cerebral blood flow deprivation. 1) The cytochrome oxidase activity was affected only in the recovery period after one hour ischemia and after 5 hours of continuous ischemia. At that time the activity of cytochrome oxidase was significantly reduced when compared to the controls. In contrast, no significant changes in the activity of acetylcholinesterase were observed in the experimental as compared to control gerbils. 2) Both enzymes, the cytochrome oxidase and acetylcholinesterase were transiently reduced in the animals anesthetized with pentobarbital. This project is completed.